U.S. patent application number 11/644603 was filed with the patent office on 2007-07-12 for specimen imaging apparatus and specimen analyzer.
This patent application is currently assigned to Sysmex Corporation. Invention is credited to Tokihiro Kosaka, Ryuichi Tohma.
Application Number | 20070159687 11/644603 |
Document ID | / |
Family ID | 38232483 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070159687 |
Kind Code |
A1 |
Tohma; Ryuichi ; et
al. |
July 12, 2007 |
Specimen imaging apparatus and specimen analyzer
Abstract
A specimen imaging apparatus is provided that is capable of
improved high-speed operation compared to conventional apparatuses.
The specimen imaging apparatus is provided with a microscope for
enlarging the image of a specimen, and taking the enlarged image of
the specimen obtained by the microscope. The apparatus is provided
with a vibration detecting means for detecting a relative vibration
between the objective lens of the microscope and the specimen
mounted n the microscope, a means for focusing before the vibration
detected by the vibration detecting means has attenuated to less
than a predetermined value, and a determining means for determining
whether or not a vibration detected by the vibration detecting
means is less than a predetermined value. The specimen imaging
apparatus is configured so as to take the enlarged image of a
specimen when the determining means has determined that the
vibration is less than a predetermined value.
Inventors: |
Tohma; Ryuichi; (Akashi-shi,
JP) ; Kosaka; Tokihiro; (Kakogawa-shi, JP) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
Sysmex Corporation
|
Family ID: |
38232483 |
Appl. No.: |
11/644603 |
Filed: |
December 22, 2006 |
Current U.S.
Class: |
359/368 |
Current CPC
Class: |
G02B 21/365 20130101;
G02B 21/244 20130101 |
Class at
Publication: |
359/368 |
International
Class: |
G02B 21/00 20060101
G02B021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2005 |
JP |
2005-369459 |
Claims
1. A specimen imaging apparatus for taking a magnified image of
specimen, comprising: a microscope, comprising an objective lens,
for magnifying an image of a specimen; a vibration detector for
detecting relative vibration between the specimen and the objective
lens of the microscope; and an imaging device for taking the image
of the specimen magnified by the microscope based on the relative
vibration detected by the vibration detector.
2. The specimen imaging apparatus according to claim 1, further
comprises a controller for determining whether or not an amplitude
of the relative vibration is smaller than a predetermined value,
wherein the imaging device is configured to take the image of the
specimen when the controller determines that the amplitude of the
relative vibration is smaller than the predetermined value.
3. The specimen imaging apparatus according to claim 1, wherein the
vibration detector comprises at least one of light receiving device
having a plurality of light receiving element for receiving a light
passing through the objective lens, and the vibration detector is
configured to detect the relative vibration based on amount of
light received by the light receiving elements.
4. The specimen imaging apparatus according to claim 3, wherein the
vibration detector is configured to detect an amplitude of an
element of the relative vibration which is related to an optical
axis direction at the specimen.
5. The specimen imaging apparatus according to claim 4, wherein two
of the light receiving devices are respectively disposed at
positions of mutually different optical distances from the
specimen; and the vibration detector is configured to obtain the
difference of focusing levels of the two of the light receiving
devices and detect the amplitude of the element of the relative
vibration based on the time fluctuation of the obtained difference
of the focusing levels.
6. The specimen imaging apparatus according to claim 3, wherein the
vibration detector is configured so as to detect an amplitude of an
element of the relative vibration which is related to a direction
perpendicular to an optical axis direction at the specimen.
7. The specimen imaging apparatus according to claim 6, wherein the
vibration detector obtains the difference of light receiving levels
of the same light receiving element of the light receiving device
at different times and detects the amplitude of the element of the
relative vibration based on the obtained difference of the light
receiving levels.
8. The specimen imaging apparatus according to claim 1, further
comprising: a holder for holding a specimen; and a moving device
for moving the holder.
9. The specimen imaging apparatus according to claim 8, wherein the
moving device is configured so as to move the holder in at least a
direction perpendicular to an optical axis direction at the
specimen.
10. The specimen imaging apparatus according to claim 2, further
comprising: inference means for inferring a focal point of the
objective lens when the amplitude of the relative vibration is
smaller than the predetermined value, while the relative vibration
remains; and a focusing device for focusing the microscope to the
focal point inferred by the inference means, while the relative
vibration remains.
11. A specimen imaging apparatus for taking a magnified image of
specimen, comprising: a microscope, comprising an objective lens,
for magnifying an image of a specimen; a moving device for moving
specimen to be imaged; a cell detecting section for detecting a
cell in the specimen moved by the moving device; a focusing device
for focusing the microscope on the specimen; a vibration detector
for detecting relative vibration between the specimen and the
objective lens of the microscope; and an imaging device for taking
the image of the cell detected by the cell detecting section based
on the relative vibration detected by the vibration detector.
12. The specimen imaging apparatus according to claim 11, further
comprises a controller for determining whether or not an amplitude
of the relative vibration is smaller than a predetermined value,
wherein the imaging device is configured to take the image of the
cell when the controller determines that the amplitude of the
relative vibration is smaller than the predetermined value.
13. A specimen imaging apparatus for taking a magnified image of
specimen, comprising: a microscope, comprising an objective lens,
for magnifying an image of a specimen; and a monitoring section for
monitoring relative vibration between the specimen and the
objective lens of the microscope.
14. The specimen imaging apparatus according to claim 13, further
comprising at least one light receiving device having a plurality
of light receiving elements for receiving light passing through the
objective lens, wherein the monitoring section is configured to
detect the relative vibration based on a light receiving level of
the light receiving device.
15. A specimen analyzer comprising: a microscope, comprising an
objective lens, for magnifying an image of a specimen; a vibration
detector for detecting relative vibration between the specimen and
the objective lens of the microscope; an imaging device for taking
the image of the specimen magnified by the microscope based on the
relative vibration detected by the vibration detector; and an
analyzing section for analyzing the specimen based on the image of
the specimen taken by the imaging device.
16. The specimen analyzer according to claim 15, wherein the
specimen is blood specimen and the analyzing section is configured
to analyze the blood specimen based on the magnified image of blood
cells included in the blood specimen.
17. A specimen analyzer comprising: a microscope, comprising an
objective lens, for magnifying an image of a specimen; a moving
device for moving specimen to be imaged; a cell detecting section
for detecting a cell in the specimen moved by the moving device; a
focusing device for focusing the microscope on the specimen; a
vibration detector for detecting relative vibration between the
specimen and the objective lens of the microscope; an imaging
device for taking the image of the cell detected by the cell
detecting section based on the relative vibration detected by the
vibration detector; and an analyzing section for analyzing the
specimen based on the image of the specimen taken by the imaging
device.
18. The specimen analyzer according to claim 17, wherein the
specimen is blood specimen and the analyzing section is configured
to analyze the blood specimen based on the magnified image of blood
cells included in the blood specimen.
19. A specimen analyzer comprising: a microscope, comprising an
objective lens, for magnifying an image of a specimen; a monitoring
section for monitoring relative vibration between the specimen and
the objective lens of the microscope; an imaging device for taking
the image of the specimen magnified by the microscope based on the
relative vibration monitored by the monitoring section; and an
analyzing section for analyzing the specimen based on the image of
the specimen taken by the imaging device.
20. The specimen analyzer according to claim 19, wherein the
specimen is blood specimen and the analyzing section is configured
to analyze the blood specimen based on the magnified image of blood
cells included in the blood specimen.
Description
[0001] This application claims priority under 35 U.S.C. .sctn.119
to Japanese Patent Application No. JP2005-369459 filed Dec. 22,
2005, the entire content of which is hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a specimen imaging
apparatus and specimen analyzer.
BACKGROUND OF THE INVENTION
[0003] Blood cell analyzers for classifying and counting blood
cells are provided with an automatic microscope, a means for taking
an image of a cell that has been enlarged by the microscope, and an
image processor for processing the obtained image and obtaining
desired analysis information such as the number of blood cells of
each classification (for example, refer to Japanese Laid-Open
Patent Publication No. 7-20124).
[0004] The apparatus disclosed in Japanese Laid-Open Patent
Publication No. 7-20124 is provided with a microscope for enlarging
blood cells smeared on a slide glass, and a color television camera
for taking the microscope image. The slide glass with the blood
smear is installed on the stage of the microscope, the stage is
displaced in the XY direction by the stage drive circuit to adjust
the position of the slide glass on the stage. Furthermore, an
objective lens is displaced vertically (Z-axis direction) by a
focus drive circuit to adjust the focal position by auto focusing.
The image from the microscope is taken by the color television
camera, and the blood cell image is displayed on an RGB
monitor.
[0005] Although this type of blood cell analyzer moves the stage to
adjust the position of the slide glass, inertia may cause the stage
to vibrate when the stage is stopped after positional adjustment.
Then, when the auto focusing is performed prior to the attenuation
of the stage vibration, the lens cannot be accurately focused on
the specimen on the slide glass. Moreover, when imaging is executed
before the vibration has attenuated, defocusing or image blurring
occur in the obtained image. Therefore, in this type of
conventional apparatus, the apparatus waits for a predetermined
time until the vibration has attenuated after the stage has
stopped, then auto focusing is executed and thereafter the enlarged
image is obtained.
[0006] In conventional blood cell analyzers, however, sufficient
waiting time must be ensured for the attenuation of the vibration
in order to reliably attenuate stage vibration and take a clear
enlarged image without blurring, thus slowing down the operation
(processing speed) of the apparatus. In addition, since the
vibration of the stage can not be detected, it is impossible to
determine whether or not the vibration has attenuated, such that
imaging may occur before the vibration has attenuated.
SUMMARY OF THE INVENTION
[0007] The scope of the present invention is defined solely by the
appended claims, and is not affected to any degree by the
statements within this summary.
[0008] The first aspect of the present invention relates to a
specimen imaging apparatus for taking a magnified image of
specimen, comprising:
[0009] a microscope, comprising an objective lens, for magnifying
an image of a specimen;
[0010] a vibration detector for detecting relative vibration
between the specimen and the objective lens of the microscope;
and
[0011] an imaging device for taking the image of the specimen
magnified by the microscope based on the relative vibration
detected by the vibration detector.
[0012] The second aspect of the present invention relates to a
specimen imaging apparatus for taking a magnified image of
specimen, comprising:
[0013] a microscope, comprising an objective lens, for magnifying
an image of a specimen;
[0014] a moving device for moving specimen to be imaged;
[0015] a cell detecting section for detecting a cell in the
specimen moved by the moving device;
[0016] a focusing device for focusing the microscope on the
specimen;
[0017] a vibration detector for detecting relative vibration
between the specimen and the objective lens of the microscope;
and
[0018] an imaging device for taking the image of the cell detected
by the cell detecting section based on the relative vibration
detected by the vibration detector.
[0019] The third aspect of the present invention relates to a
specimen imaging apparatus for taking a magnified image of
specimen, comprising:
[0020] a microscope, comprising an objective lens, for magnifying
an image of a specimen; and
[0021] a monitoring section for monitoring relative vibration
between the specimen and the objective lens of the microscope.
[0022] The fourth aspect of the present invention relates to a
specimen analyzer comprising:
[0023] a microscope, comprising an objective lens, for magnifying
an image of a specimen;
[0024] a vibration detector for detecting relative vibration
between the specimen and the objective lens of the microscope;
[0025] an imaging device for taking the image of the specimen
magnified by the microscope based on the relative vibration
detected by the vibration detector; and
[0026] an analyzing section for analyzing the specimen based on the
image of the specimen taken by the imaging device.
[0027] The fifth aspect of the present invention relates to a
specimen analyzer comprising:
[0028] a microscope, comprising an objective lens, for magnifying
an image of a specimen;
[0029] a moving device for moving specimen to be imaged;
[0030] a cell detecting section for detecting a cell in the
specimen moved by the moving device;
[0031] a focusing device for focusing the microscope on the
specimen;
[0032] a vibration detector for detecting relative vibration
between the specimen and the objective lens of the microscope;
[0033] an imaging device for taking the image of the cell detected
by the cell detecting section based on the relative vibration
detected by the vibration detector; and
[0034] an analyzing section for analyzing the specimen based on the
image of the specimen taken by the imaging device.
[0035] The sixth aspect of the present invention relates to a
specimen analyzer comprising:
[0036] a microscope, comprising an objective lens, for magnifying
an image of a specimen;
[0037] a monitoring section for monitoring relative vibration
between the specimen and the objective lens of the microscope;
[0038] an imaging device for taking the image of the specimen
magnified by the microscope based on the relative vibration
monitored by the monitoring section; and
[0039] an analyzing section for analyzing the specimen based on the
image of the specimen taken by the imaging device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is a block diagram showing the structure of a blood
specimen analyzer that includes an embodiment of the specimen
imaging apparatus;
[0041] FIG. 2(a) the pattern of scanning a specimen on a slide
glass;
[0042] FIG. 2(b) shows the field of vision of a line sensor and a
blood cell on its periphery;
[0043] FIG. 2(c) shows the line sensor detection signals;
[0044] FIG. 3 is a perspective view of the essential parts of the
specimen imaging apparatus;
[0045] FIG. 4 illustrates the layout of the two focusing
sensors;
[0046] FIG. 5(a) shows a signal waveform of the focusing sensor at
a position shifted from the focal position;
[0047] FIG. 5(b) shows a signal waveform of the focusing sensor at
the focal position;
[0048] FIG. 6 shows the relationship between amount of movement of
the objective lens and the difference integration value, that is,
the value of the integrated difference of the signals of adjacent
pixels of the two focusing sensors;
[0049] FIG. 7 shows the relationship between amount of movement of
the objective lens and the difference of the difference integration
values of the two focusing sensors; and
[0050] FIG. 8 shows the residual vibration movement directly after
the stage is stopped.
DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED
EMBODIMENTS
[0051] The embodiment of the specimen imaging apparatus and
specimen analyzer are described hereinafter based on the
drawings.
[0052] FIG. 1 is a block diagram showing the structure of a blood
specimen analyzer that includes an embodiment of the specimen
imaging apparatus. FIG. 1 schematically shows the structure of the
apparatus; the actual layout of the sensors and slide cassette and
the like has been altered slightly to facilitate understanding. For
example, although the WBC detecting sensor and the focusing sensor
are shown in a vertical arrangement in FIG. 1, the actual
arrangement has both sensors disposed within the same approximately
plane, as shown in FIG. 3, which is described later.
[0053] The blood specimen analyzer is configured by a specimen
imaging apparatus A for taking an enlarged image of a blood
specimen that has been focused by auto focusing, an image
processing apparatus B for processing the obtained image,
classifying the white blood cells in the blood, and counting the
number of white blood cells of each classification, and a personal
computer C provided with an input unit 30 connected to the image
processing apparatus for inputting various types of instructions
for analysis, and a display unit 31 for displaying the obtained
images and analysis results and the like. Moreover, the image
processing apparatus B and personal computer C may be integrated so
as to include the functions of the image processing apparatus B
within the personal computer C, rather than have them separate.
[0054] The specimen imaging apparatus A is provided with an
objective lens 3 configuring part of a microscope lens system for
enlarging the image of blood (specimen) thinly smeared on a slide
glass disposed on an XY stage 1 (refer to FIG. 3). The XY stage 1,
which is a holding part for holding a specimen, is controlled by an
XY stage drive circuit 5, and is moved forward and back and
laterally (X direction and Y direction) by a drive part (not shown
in the drawing) that is a moving device; moreover, the objective
lens 3 is moved substantially vertically (Z direction) by a drive
part (not shown in the drawing) that is controlled by an objective
lens drive circuit 4.
[0055] The slide glass 2 is housed inside a slide cassette 7 that
accommodated a plurality of stacked slides, and the slide cassette
7 is transported by a transporting part (not shown in the drawing)
whose actuation is controlled by a cassette transport drive circuit
6. A chuck 8 for holding the slide glass 2 at two locations near
the bilateral ends in the lengthwise direction is provided on the
XY stage 1 so as to be capable of advancing and receding relative
to the slide glass 2 housed within the slide cassette 7 that has
been stopped at a predetermined position. Then, the chuck 8 is
advanced toward the slide cassette 7, and grips the slide glass 2
by opening and closing a hook part 8a that is capable of being
opened and closed and is formed on the leading end of the chuck 8;
a slide glass 2 is pulled from the slide cassette 7 by receding the
chuck 8, and the slide glass 2 is positioned at a predetermined
position on the XY stage 1.
[0056] A light source lamp 9 is disposed below the slide glass 2,
and the light from this lamp 9 passes through the blood on the
slide glass 2 then passes through a half mirror 10 and interference
filter 11 disposed on the optical path, then enters an auto focus
sensor (photoreceptor) 12, white blood cell (WBC) detection sensor
(photoreceptor) 13, and CCD camera 14. Then, the white blood cells
are detected by a white blood cell detecting device 20 based on the
signals of the incidence light, and an auto focus operation is
performed by an auto focus device 21. In the present embodiment,
the auto focus device is configured by the sensor 12, the auto
focus device 21, the drive part of objective lens 3, and the
objective lens drive circuit 4. An imaging controller 22 is also
provided to control the imaging, which includes transmission of an
imaging start signal, and this imaging controller 22 is provided
with a determining means for determining whether or not a relative
vibration between the specimen and the objective lens 3 has
attenuated.
[0057] The image processing apparatus B has an A/D converter 15,
characteristic extraction processor 16, and auto classification
processor 17; and the imaging signals for the image taken by the
CCD camera 14 are converted from analog signals to digital signals
by the A/D converter 15. Then, the characteristic parameters of
white blood cells are calculated by the characteristic extraction
processor 16 based on the digital signals. The characteristic
parameters include white blood cell nucleus area, number of the
nucleus, asperity of the nucleus, color tone of the nucleus,
density (uneven of density) of the nucleus, white blood cell
cytoplasm area, color tone of the cytoplasm, density (uneven of
density) of the cytoplasm, and area ratio and density ratio and the
like of the nucleus and cytoplasm. These characteristic parameters
are used to automatically classify and count the types of white
blood cells via the auto classification processor 17. Specifically,
the types of white blood cells can be gradually determined by, for
example, sequentially comparing the various characteristic
parameters of a white blood cell to determining a standard value
that has been previously determined for each parameter. Thus, the
imaged white blood cell can be classified as a type of mature white
blood cell such as lymphocyte, monocyte, eosinophil, basophil,
neutrophil (stab neutrophil, segmented neutrophil), or a type of
immature white blood cell such as blast cell, juvenile granulocyte,
atypical lymphocyte, as well as erythroblast.
[0058] The specimen imaging apparatus of the present embodiment is
provided with an auto focus function to perform focusing
automatically, and the sequence flow of the auto focus operation is
described below.
[0059] First, the white blood cells in the blood smeared on the
slide glass 2 are detected before the auto focus. This detection is
accomplished using the previously mentioned sensor 13. The sensor
13 is a line sensor with a field of view of approximately 400
.mu.m. Then, the XY stage 1 is moved in the X direction and Y
direction (refer to FIG. 2(a)) so as to have the sensor 13 scan the
slide glass 2 from one end to another in an approximate zigzag
pattern in the length direction. An interval D of the zigzag scan
in the lengthwise direction of the slide glass 2 is normally
approximately 300 .mu.m from the viewpoint of scanning efficiency
and avoiding detection omissions, and the scanning dimension H in
the width direction of the slide glass 2 normally approximately 16
mm since the width of the slide glass 2 is typically about 26
mm.
[0060] Since the nucleus of a white blood cell WBC absorbs a large
amount of the red component of light, white blood cells (WBC) and
red blood cells (RBC) can be easily differentiated by detecting the
red component. FIG. 2(b) shows the presence of a white blood cell
within the field of view of the line sensor; in this case, the red
light component of the signal detected by the line sensor is less
than a standard value S at the location at which the white blood
cell is present, as shown in FIG. 2(c). The white blood cells in
the blood can be detected using this phenomenon. It is possible to
check whether or not part of the signal indicates a white blood
cell by detecting the width W of the red component of the signal
that is less than the standard value S.
[0061] [Auto Focus (Non-Vibration Time)]
[0062] When a relative vibration is generated between the specimen
and the objective lens, the specimen imaging apparatus executes the
auto focus operation while the vibration is generated and does not
perform the auto focus operation after the vibration has
attenuated; below, the auto focus operation is first described for
the case in which a large vibration sufficient to affect image
quality is not generated.
[0063] FIG. 3 is a perspective view of the essential parts of the
specimen imaging apparatus of the present embodiment; light that
has passed through the slide glass 2 and the objective lens 3 is
directionally redirected by a prism mirror 18 and split into light
that is directed toward the CCD camera 14 by a half mirror 19, and
light that is directed toward the sensors 12 and 13. The sensor 12
is an auto focus sensor (line sensor), and is configured by two
sensors 12a and 12b. The sensor 13 is a white blood cell detection
sensor (line sensor). The sensors 12 and 13 also function as
vibration detection means for detecting a relative vibration
between the specimen and the objective lens 3 as will be described
later.
[0064] As shown in FIG. 4, the sensor 12a among the two auto focus
sensors 12a and 12b is disposed on the front side of the focal
position (position at which the view is focused). In other words,
an optical distance from the objective lens to the sensor 12a is
shorter than an optical distance from the objective lens to the
focal position. And the other sensor 12b is disposed on the rear
side of the focal position. In other words, an optical distance
from the objective lens to the sensor 12b is longer than the
optical distance from objective lens to the focal position.
[0065] The signal waveform of the sensor at the focal position is a
waveform of large amplitude, as shown in FIG. 5(b), due to the
clear contrast. And the signal waveform of the sensor at a
non-focal position is an overall moderate and small amplitude
waveform, as shown in FIG. 5(a), because the contrast is not so
sharp. Approximately 2000 pixels are typically arranged in a linear
array in a line sensor, and a value of an integrated signal
difference between adjacent pixels of the line sensor (referred to
below as a difference integration value) increase as the focus
improves.
[0066] FIG. 6 shows the respective difference integration values of
the two sensors when the amount of movement of the objective lens 3
is plotted on the horizontal axis. Ai represents the difference
integration value of the sensor 12a disposed on the front side of
the focus point, and Bi represents the difference integration value
of the sensor 12b disposed on the rear side of the focus point. In
the case of the sensor 12a, focus is attained and the difference
integration value Ai has a peak value when the objective lens is
moved upward (i.e. the objective lens is moved away from the slide
glass) by about 2 .mu.m from a focal position of the objective lens
at which a focal point of the objective lens is on the CCD camera
14. In the case of the sensor 12b, focus is attained and the
difference integration value Bi has a peak value when the objective
lens is moved downward (i.e. the objective lens is moved toward the
slide glass) by about 2 .mu.m from the focal position of the
objective lens.
[0067] When only one sensor, for example, only the sensor 12a, is
used for focusing, it is impossible to determine the moving
direction of the objective lens for obtaining the peak value of the
difference integration value Ai. In this case, the objective lens
must be moved by trial and error to achieve focusing, such that the
auto focus operation requires considerable time. Conversely, when
two sensors in the previously described disposition are used for
focusing and the difference integration values of the two sensors
(Ai-Bi) are determined, as shown in FIG. 7, it is possible to
perform auto focusing in a short time. That is, when the focal
position is Ai-Bi=0 by adjusting the microscope beforehand so as to
match the focal point of the objective lens with the specimen on
the slide glass, auto focusing can be performed simply by moving
the objective lens in a direction toward Ai-Bi=0,
[0068] [Auto Focus (Vibration Time)]
[0069] As shown in FIG. 7, the value (Ai-Bi) at a particular time
has a single value, and when, for example, a table or base on which
the automatic microscope is installed is jarred by someone or
something, or when the XY stage is moved for white blood cell
detection and the XY stage is stopped after detection, a relative
vibration is generated between microscope lens and the slide glass
disposed on the XY stage, that is, between the specimen and the
objective lens, such that the (Ai-Bi) value also fluctuates for the
same period as the vibration. FIG. 8 shows the (Ai-Bi) value
directly after the XY stage has stopped following white blood cell
detection. Since the (Ai-Bi) value wavers between positive and
negative values until the residual vibration has attenuated, auto
focusing can not be performed because the direction on the Z-axis
in which to move the object lens can not be determined based on the
(Ai-Bi) value during this vibration.
[0070] However, since the (Ai-Bi) value only fluctuates with the
same magnitude in the positive and negative sides about a value
attained during non-vibration time (the value when there is no
vibration), it is possible to infer an approximate value of the
(Ai-Bi) value when the vibration has attenuated by obtaining a
moving average value of the (Ai-Bi) so as to include one period of
the fluctuation. In other words, the focal position when the
vibration has attenuated can be inferred, and the objective lens
can be moved such that the lens focus point matches the specimen on
the slide glass.
[0071] The period of relative vibration between the slide glass and
the objective lens of the microscope differs depending on a natural
frequency which is determined by the weight and material of the
apparatus and the assembly of the device. The natural frequency of
the designed specimen imaging apparatus is determined beforehand,
so that the moving average can be determined by averaging (Ai-Bi)
by the values of the periods of the natural frequency. For example,
if the vibration period of the specimen imaging apparatus is 5
msec, the (Ai-Bi) value is calculated for each 1 msec, and the
values of the past one period are averaged by averaging the nearest
five values, such that whether or not the (Ai-Bi) value (the value
during the vibration attenuation time) is positive or negative can
be determined by the obtained moving average value. Then, the auto
focus direction can be understood accurately and the objective lens
can be moved based on the moving average value regardless of
whether the vibration is on-going, and the auto focusing can be
started because the amount of movement of the objective lens can be
inferred. The focal position can be inferred even at the point in
time when the vibration is greatest and near 20 msec as shown in
FIG. 8. Auto focusing according to the decrease (attenuation) of
the vibration is completed by calculating the moving average value
and repeating the objective lens movement a plurality of times
based on that calculated value.
[0072] Thus, if a relative vibration between the microscope lens
and the slide glass disposed on the XY stage is being generated by
someone or something jarring the base or table on which the
specimen imaging apparatus is installed, the specimen imaging
apparatus of the present embodiment executes the auto focus
operation while avoiding the effects of vibration. Consequently,
the time necessary for the auto focus operation of the present
embodiment can be greatly reduced compared to time necessary for an
auto focus operation is started after the vibration has attenuated.
Specifically, the auto focus operation is conventionally executed
after vibration has attenuated by waiting approximately 50 msec
after the white blood cells are detected and the XY stage has
stopped. On the other hands, the present embodiment allows the auto
focus operation to be executed during the vibration, thereby
reducing the time necessary for auto focusing at least by the
amount of waiting time. As a result, processing speed is increased
when an enlarged specimen image is taken and various processes are
performed based on the obtained image.
[0073] [Imaging Execution]
[0074] The specimen imaging apparatus of the present embodiment
differs from a conventional apparatus that performs an auto focus
operation and takes an image after the XY stage has stopped and a
predetermined time has been awaited for the residual vibration to
attenuate. The specimen imaging apparatus of the present embodiment
is provided with means for detecting a relative vibration between
the specimen and the objective lens that is generated after the XY
stage stops so as to take an enlarged image of a specimen when a
vibration has been determined to have attenuated.
[0075] The attenuation of the vibration is determined in the
following manner. First, the sensors 12a and 12b are used to
determine whether or not the vibration element in the optical axis
direction has attenuated. The sensors 12a and 12b at disposed at
mutually different positions. An optical distance between the
position of sensor 12a and the specimen is different from an
optical distance between the position of sensor 12b and the
specimen. The difference in the focusing level between the two
sensors 12a and 12b is calculated during auto focusing, and the
difference in focusing level is also used for determining vibration
attenuation. That is, when a vibration is generated in the optical
axis direction, the optical distance between the specimen and the
objective lens of the microscope fluctuates in conjunction with
this vibration. Then, when the sensors are respectively disposed at
positions that are mutually different optical distances from the
specimen, the magnitude of the vibration element in the optical
axis direction can be detected by determining the difference
between the maximum value and minimum value of the difference in
focusing levels within a predetermined time since the difference in
focusing levels (contrast) of the two sensors fluctuates in
accordance with the vibration (refer to FIG. 8). For example, one
period (normally, approximately 3-10 msec) of the vibration of the
specimen imaging apparatus can be set as the predetermined period.
Then, the difference between the maximum value and the minimum
value of the difference in focusing levels can be determined
beforehand as a standard value when the vibration has actually been
shielded, and it is possible to determine that the vibration is
attenuated when a detected value is less than a predetermined value
(for example, double the standard value). In the present
embodiment, the magnitude of the vibration element in the optical
axis direction can be monitored in this way.
[0076] The sensor 13 for detecting white blood cell (WBC) is used
to determine the magnitude of the vibration element in a direction
perpendicular to the optical axis direction at the specimen, so as
to determine whether or not the vibration has attenuated. The
difference in the amount of received light of the same pixel of the
sensor 13 at different time points is calculated, and the magnitude
of the vibration element in a direction perpendicular to the
optical axis direction is detected based on the difference in the
amount of received light. Although one pixel of the sensor 13 (a
plurality of pixels are disposed in linear array) receives light
from one point on the specimen when a vibration is not generated in
a direction perpendicular to the optical axis direction, a single
pixel of the sensor 13 receives light from different parts on the
specimen when a vibration is generated in a direction perpendicular
to the optical axis direction because the specimen shifts in the
perpendicular direction. Therefore, the magnitude of the vibration
element in a direction perpendicular to the optical axis direction
is detected by determining the difference in the amount of light
received by the same pixel of the photoreceptor part at different
time points. Specifically, difference between amount of light
received by a pixel at time point t0 and amount of light received
by the pixel at time point t1 is determined. The process is
performed with respective to a plurality of pixels, for example 500
pixels, in the sensor 13 having 2,000 pixels and the sum T1 of the
differences is determined. Then, the sum Tn for a predetermined
time interval is determined, and it is possible to determine that
the vibration is attenuated when an average value of the sum in one
period of the vibration of the apparatus is less than a
predetermined value to exclude errors (the predetermined value can
be determined in the same manner as the predetermined value for
detecting a vibration in the optical axis direction). In the
present embodiment, the vibration in a direction perpendicular to
the optical axis direction can be monitored in this way. Then,
imaging is executed via the CCD camera 14 after the vibration in
the optical axis direction has been determined to have attenuated
by monitoring the vibration in the optical axis direction, and
after the vibration has been determined to have attenuated in a
direction perpendicular to the optical axis direction. When a
vibration is generated in the optical axis direction, the distance
fluctuates between the specimen and the objective lens, such that
when imaging is executed before the vibration has attenuated, the
focus point shifts due to the vibration and causes defocusing, and
a sharp image can not be obtained. Furthermore, since the relative
positional relationship between the specimen and the optical axis
fluctuates when a vibration is generated in a direction
perpendicular to the optical axis direction, blurring of the image
occurs when imaging is performed before the vibration that includes
the this directional element has attenuated. However, a sharp image
without defocusing and blurring can be obtained by respectively
monitoring the vibration element in the optical axis direction and
a direction perpendicular to the optical axis direction, and
performing imaging after the vibrations have attenuated.
[0077] Blood cells are imaged in the embodiment described above,
but since blood cells are extremely minute, the image of the sample
including these cells must be enlarged to a high magnification
(approximately several hundred times) by a microscope. Therefore, a
small vibration may have a great effect on the apparatus.
Furthermore, the specimen is moved by a moving device, and the
operation of this moving device may also generate a vibration.
Sharp images can be obtained by preventing defocusing and blurring
of an image caused by vibration by providing a vibration detection
means to detect a relative vibration between the specimen and the
objective lens and taking an enlarged image of a cell based on the
vibration detected by the vibration detection means, and the speed
of the operation of the apparatus can be further increased compared
to a conventional apparatus by reducing the time from the
attenuation of vibration to imaging.
[0078] Although auto focusing is performed using two sensors 12a
and 12b in the present embodiment, auto focusing may also be
performed using a single sensor. Since the peak value of the
difference integration value Ai can not be determined when only one
sensor, for example, only the sensor 12a, is used, the objective
lens must be moved by trial and error to accomplish focusing, and
this arrangement thus increases the time of the auto focus
operation, but has the advantage of simplifying the structure by
reducing the number of sensors. Since the focusing level fluctuates
in conjunction with the vibration even when a single sensor is
used, the vibration can be detected by detecting the focusing
level.
[0079] Although focusing is accomplished by moving the objective
lens vertically in the above embodiment, it is also possible to
move the XY stage itself vertically. Furthermore, the period of
relative vibration between the slide glass and the microscope lens
may be measured automatically during the assembly of the specimen
imaging operation device and the number of values (moving average
at nearby points) for determining a moving average value and time
interval for calculating the (Ai-Bi) value based on the measured
vibration period value can also be determined. Additionally, the
consecutive (Ai-Bi) value over 8 msec can be determined each time
the XY stage stops, and this value can be subjected to FFT
frequency analysis to calculate the length of one period by
determining the frequency of maximum intensity (amplitude), and
determining the number of values for determining the moving average
value and time interval for calculating the (Ai-Bi) value based on
the length of one period.
[0080] Although the present embodiment is provided with an auto
focus function, the present invention is also applicable to a
specimen imaging apparatus that is not provided with an auto focus
function inasmuch as sharp images can be obtained by avoiding
blurring and defocusing of and image caused by vibration, and
reducing the time fro the attenuation of a vibration to imaging
compared to conventional apparatus since and enlarged image of a
specimen can be taken when it has been determined that a vibration
detected by the vibration detection means has attenuated.
[0081] The foregoing detailed description and accompanying drawings
have been provided by way of explanation and illustration, and are
not intended to limit the scope of the appended claims. Many
variations in the presently preferred embodiments illustrated
herein will be obvious to one of ordinary skill in the art, and
remain within the scope of the appended claims and their
equivalents.
* * * * *